Infants and other incontinent individuals wear absorbent articles such as diapers to absorb and retain urine and other body exudates. Absorbent articles function both to contain the discharged materials and to isolate these materials from the body of the wearer and from the wearer's garments and bed clothing. Disposable absorbent articles having many different basic designs are described, for example, in U.S. Pat. No. Re. 26,151 and U.S. Pat. No. 3,860,003.
Diapers that have achieved increasing commercial success in recent years are pull-on pant-type diapers or training pants. Diapers are used with infants prior to toilet training. The training pant is intended for use when the child has reached an age at which he or she is ready to graduate to an underpant type of garment as a replacement for disposable diapers previously used. Training pants have a “closed” chassis configuration, in which the chassis is adapted to be pulled on over the legs and lower torso of the wearer without any additional fastening steps.
Closed chassis diapers can be manufactured using a unibody design or a multi-piece design. In a multi-piece design, there are typically at least three chassis components that form the diaper: a crotch component, a front ear component, and a back ear component. Very generally, the crotch component extends in the long direction from the front to the back, and the front ear component and the back ear component extend in the long direction from one side to the other. The front ear component is attached to a front edge of the crotch component and the rear component is attached to a rear edge of the crotch component. A generally hour-glass configuration is thus achieved. A unibody design involves a single component that is shaped as desired. Thus, a rectangular piece may be shaped by notching the sides in the crotch area. Regardless of whether a multi-piece design or a unibody design is used, the front ear is seamed to the back ear to form the closed chassis.
Absorbent articles may have manually tearable side seams. The seams may be butt-type seams or overlapping side seams. An underpant may be manufactured from a blank cut to a suitable configuration. Layers of the diaper are built up on the blank cut and, after being fully assembled, the blank is folded along its central transverse area and the sides of the front and rear panels are seamed together to form the finished underpant. Alternatively, the seams may be formed by folding the chassis in the crotch portion so that the longitudinal side regions of the front portion and rear portion are superposed to form seaming areas, and then treating each seaming area with ultrasonic energy to sever the material in the seaming area in a first area while simultaneously bonding the material of the seaming area in a marginal area adjacent the first area to form a flangeless seam. This may form a splice between the front portion and the rear portion of the chassis.
It would be advantageous to provide a method for producing an article such as a training pant having side seams that produces the training pants at a high rate. It would further be advantageous to provide an apparatus for carrying out such method, which apparatus is of relatively simple construction, and allows high-speed formation of the side seams.